In the prior art, various resins such as polyester and polyurethane are often modified by incorporating silicone therein to improve their properties or to impart silicone properties to them. For the manufacture of silicone modified materials, there are known a variety of organic silicon compounds for silicone modification or introduction. There is a need for an organic silicon compound which can be reacted with polyester, polyurethane or similar resins having a carboxyl, chloroformyl or isocyanate group for silicone modification of the resins for improving their heat resistance, weathering resistance, humidity resistance, dyeability, oxygen plasma resistance and the like so that the modified resins are useful as coating materials and semiconductor fine processing materials such as photoresist.